Method of recording and reproducing sound.



F. W. H. CLAY.

METHOD 0E. RECORDING AND EEPBODUOING SOUND. APPLiOATION FILEDc0T.2s,19om

1,101,906. Y Patented June .30, 1914,

FIG.

T mvamon ATTORNEY.

UNITED STATES PATENT orrros.

FRANCIS '.W., H'- CLAY, OF PITTSBURGH, PENNSYLVANIA.

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Specification of Letters Patent.

- Eastman, 1914.

Application filed October 25, 19cm Serial 110,339,112.

primary .object is. to smooth the irregu larities' of natural sound waverecords, and

vavoid the noises incident to :the reproduction, etc.

Other objects will appear hereinafter. I have here illustrated themethod as applied to instruments such as phonograp s other applicationssuch as telephoning. I

In the accompanying drawing Figure 1 is a diagram illustrating v soundon a wax cylinder, and 2 amodification of the apparatus. Fig. ;3illustrates the apparatus which may be used for recording on flatsurfaces. :Fig. 4 illustrates a. construction of a sound actuateddiaphragm and Fig. 5 illustrates another modification for dampeningirregular waves.

Fig. -6 illustrates some forms of soundwaves. Fig. 7 illustrates theapplicationof the invention to telephoning. x

In the study of sound waves I have dis-- covered that the probable cause'of impure tones is the superimposition, upon the wave form, ofirregular subsidiary waves. And a pure tone is distinguished from'animpure tone not. so much by the absence of the superimposed waves, as bytheir being regular. The tympanum of theear is probably in incessantcomplicated motion and the'physiological effect of a ;pure tone islargely due to submerging the irregular motions by cans ing the hearingorgans to swing in regular rather than irregular order. In the sound.records at present used in phonographs,etc.,

the reproducing diaphragm never vibrates without both fundamental andovertone, and in addition undesirable and minute superposed vibrationsof irregular :form. l his is due in part to the imperfections in thestructure of the record, and in part to the independent and irregularvibrations of the diaphragm. It is obvious that if the diaphragm isswinging with are lar-periodicity, even if it makes an inaudi le-vibration, this will submerge or drown out the noisy". sounds, fornoise difiers from musical sound only by the recording of v reason ofthe irregularity of vibration. It

is the object of my invention to accomplish this end either by alteringthe shape of the sound record,-or;by impressing minute regu-. larvibrations on the reproducing diaphragm. Y q

Referring first to Fig. 6, a puretone might be illustrated by the formA, but owing to mechanical imperfections the actua'l form of the wavesproduced by phonographs is that shown at Bi. At C is illustrated a formof waveinwhich the superimposed minute -vibrationsi on the fundamentaland overtone wave form are made Yregular rather than irregular. In other;words if the cause of the noise," that is, the and gramophones,butitobviously has many I I irregular forms on the wave B, can be reduced toalregular periodicity as in C, this superposed formcan still be so smallas to In other words a, wave form be inaudible. such as C would-produceon the ear the effect ,of a simple and perfectly smooth sound,.be-

cause the ear cannot respond to the small undulations C, while theycould perceive the irregular vibrations B because of the irregular beatsproduced bythem in combination with the fundamental;

In Fig. 1 the wax cylinder 7 upon which .the sound record is anade bythe motion of the'cutting tool 8, which in turn is. moved waves, musthave cut on its record which will be the resultant of all the motions ofthe diaphragm and of the varying resistance by the diaphragm "9 actuatedby the sound of the cylinder material. It is evident that v if diaphragm9 be constantly swinging at a regular rate it will not be so susceptibleto irregular motions, and it is also evident that thisregular swingingmovement would not interfere with the larger movement due to the soundwaves. Suppose for example the diaphragm cutting too were throughout therecording process swinging with frequency above limits of audition,somewhere about 40,000 per second" All the audible sound waves desiredwould have a periodicity not .greater than about 10,000 and thesupplementary swingingof the diaphragm might be made as low as twentythousand in some instances. Any convenient means can be' used iorsuoerposing the supplementary vibrations and I have illustrated amagnetic coil 10 which is excited by an alternating.

current source 11 having a periodicity above the limits of audition. Thediaphragm 9 of course may be of iron and thereupon it will be keptconstantly s\\-'inging at this high frequency, without interfering withits response to the ordinary sound waves. Various forms of apparatus maybe used for supplying the supplementary vibration; as in. l 2 themagnetic ring 12 may be eX- cited by coil [3 electrically, and operateon the edges of the recording disk 9. Mechanical means of course mightequally Well be used for vibrating the disk.

In Fig. 3 is a form of apparatus for re cording on a fiat surface andhere the diaphragm may be operated on by tuning fork l4 kept vibratingby means of an electrical interrupter 15. The recording point 17 willthus be in constant motion at a rate of say 5,000- per second, and thisswinging will drown out the tendency to move under the influence ofirregular sound waves. By

reason of the momentum also, the recording point obviously will not bein responsive condition for making irregular movements. In both of theforms of apparatus it will be observed also that the varying resistanceto cutting, in the material of the cylinder or plate, will be renderedunvarying by reason of the energy of the supplementary vibration, andthis will leave the instrument freer to respond to the actual soundwaves being recorded. Conversely, in reproducing the sound waves, thestylus and diaphragm will manifestly be kept in the state of extremelyrapid and regular vibration of too high frequency to beheard, and thismotion will by reason of the momentum prevent any response to irregularnoises. The same object of submerging irregular vibrations may beaccomplished by covering the diaphragm with a large number of smallelements having a definite period of vibration, which will serve todampen all motions of the diaphragm, except those in harmony withthemselves, and thus purify the tone. Thus in Fig. 4; a series of wiresA, B, C, D, E, F, each of a length and weight to respond to a simplenote, are attached to the diaphragm which is used either for recordingor reproducing,

For recording various other methods of dampening irregular vibrations-.may .of course be used and. I have illustrated in Fig. 5 one in whicha series of independent diaphragms 18 are placed side by side andcommunicating their motion. by elastic links 19, so that the recordingstylus 8 will be influenced by the cumulative effect of the variousdiaphragms,it being understood that the space between diaphragms is openand the sound waves are directed in at the point S. Thus the irregularvibrations of the several diaphragms will mutually suppress each other,since the whole set cannot affect the stylus except by acting in unison.Another use of the dampening devices is when will cause sound beatswhich will increase the amplitude of the desired sounds, and by thismeans such devices as amplifying horns may be done away with, it beingunderstood that a particular sound wave may be rendered louder not onlyby increasing the amplitude of motion but by sharpening the apex of thewave. If therefore in the recording device the subsidiary vibrations aremade to be a multipleto each of the natural musical tones there will bea regular beat at the crest of each musical tone wave between thefundamental and subsidiary impressed waves. This will amplify the soundand reproduction. Obviously this method of suppressing irregularvibrations may be applied to other instruments such as tele phones. Forexample if a telephone re ceiver diaphragm be kept in constant vibrationat a rate above the limit of audition, this will dampen or cancel allirregular vibi itions without interfering w'th the slower swing of thevocal sounds, and the same method may be used also in the transmitter.Various other uses of this method will occur to those familiar with theart and need not be here set forth in detail.

' I believe I am the first to discover that noise may be suppressed bysubstituting for the noise wave an inaudible regular wave.

However, the impressed supplementary wave may of course be made audiblewith some good effects. The fundamental idea of the invention may beillustrated mechanically by saying that it is the object of thesupplementary regular waves to comb out the irregularities from theregular sound waves. While I am also the original inventor of means forimpressing upon a sound recording instrument a supplementary regularvibration of inaudible frequency, the apparatus herein disclosed is notclaimed herein, but

111 my co-pending application No. 724,744

filed Oc 9, 1912.

Having thus described my invention and illustrated its use what I claimas new and desire to secure by Letters Patent is the following 1. Themethod of recording sound Waves which comprises impressing upon theordinary motions of the recording instrument, a supplementary regularseries of high frequency vibrations.

2. The method which consists in suppressing noises by forcing avibrating member to regular vibration of higher frequency than the soundwaves independently of the source of the sound wave frequency.

3. The method of recording sound which consists in vibrating a recordinginstrument by the agency of sound waves and impressing on it a regularvibration of higher frequency than that of audible sound.

4. A sound record having in addition to they are tuned to differentfrequencies, they 1 the undulations of the recorded sounds, a

independent of and higher than the sound wave frequencies.

In testimony whereof I have hereunder signzed myname this Qth day ofOctober, 190

FRANCIS W. H. CLAY.

Witnesses:

C. M. CLARKE, FRED STAUB.

